Open the Customize window to set which toolbar items to display:
*Firefox > Options > Toolbar Layout
*View > Toolbars > Customize
*Check that "Bookmarks Toolbar items" is on the Bookmarks Toolbar
*If the "Bookmarks Toolbar items" is not on the Bookmarks Toolbar then drag it back from the toolbar palette in the customize window to the Bookmarks Toolbar
*If missing items are in the toolbar palette then drag them back from the Customize window on the toolbar
*If you do not see an item on a toolbar and in the toolbar palette then click the "Restore Default Set" button to restore the default toolbar set up
*https://support.mozilla.org/kb/How+to+customize+the+toolbar
*https://support.mozilla.org/kb/Back+and+forward+or+other+toolbar+items+are+missing
*http://kb.mozillazine.org/Toolbar_customization